 simple bash script is all that is needed.  
  #!/data/data/com.termux/files/usr/bin/bash
  #
  #  name: rsync.pictures
  #  author: cobra2
  #  The script that is used to sync pictures from a device using termux to a
server via ssh and rsync.

  from = "/data/data/con.termux/files/home/storage/shared/DCIM/Camera"

  user = "user"
  host = "user.noip.me"
  path = "/mnt/lion/pictures/pics.phone"

  rsync -rvz -e 'ssh -p 22' $from $user@$host:$path

To access the external SD card, you need the termux-API package and have to run termux-setup-storage